1. Field of the invention
The present invention relates, in general, to photomasks for the measurement of resolution of exposure equipment and, more particularly, to provide accuracy and simplicity in measuring the resolution of exposure equipment.
2. Description of the Prior Art
Generally, photolithography is one of the most important processes for manufacturing semiconductor device circuits, by which a plurality of the same circuits can be formed on one wafer at same time. Indeed, the production yield of semiconductor device is virtually dependent on photolithography. Hence, the photomasking process is required to be precise. In Particular, the photomasks used should be accurately aligned in each process of photolithography for precision in the photomasking process. A photomask for measuring resolution of exposure equipment has usually been used to measure the resolution of a pattern formed, for example, in the photo process and the etch process, and the best focal state of the exposure equipment, in addition to measuring the resolution of the exposure equipment itself.
In order to better understand the background of the invention, a description a conventional photomask for measurement of resolution of exposure equipment is given below, with reference to FIGS. 1 and 2.
Referring to FIG. 1, there is shown a part of a wafer that is sectioned by scribe lines. Active regions on the wafer are defined by scribe lines 2 in which a pattern 3 is formed in order to measure resolution of exposure equipment.
Referring to FIG. 2, there is shown in detail the pattern for measuring resolution of exposure equipment. This resolution-measuring pattern consists of a plurality of groups in which several photosensitive film patterns 4 having identical line widths are separated by a regular space. The space between the photosensitive film patterns in each group is recognized by the numeral engraved in relief or intaglio beside the patterns, which value corresponds to the size of the group. Resolution of exposure equipment can be measured by obtaining a clear photosensitive film pattern 4 of a group with the least line width.
Since such a pattern for measuring resolution of exposure equipment is detected through a microscope with the naked eye, there is always a measurement error generated each time it is measured, which makes it very difficult to find the best state of the exposure equipment. Consequently, it is virtually impossible to accurately set the minimal limit of the resolution of exposure equipment with the conventional pattern.
In addition, the conventional pattern for measuring resolution of exposure equipment becomes finer with high integration of semiconductor device, and photolithography or etch processes cause the fine pattern to peel, generating defects in the semiconductor device.